Good Afternoon John,
I also have one of the Ovenaire "Sierra" oven/oscillators.
Mine still has the octal socket and wiring with it.

Also I opened up mine and took a peek inside.
(not much to actually see unless you destroy it)

Here is the internal wiring and the external (socket) wiring:
Pin #1 - (internal - Red wire) Socket - Red wire connected to pin #4 and probably to (+) voltage.
Pin #2 - (internal - N.C.) Socket N.C.
Pin #3 - (internal - Green) Socket - Red wire.
Pin #4 - (internal - White/Red stripe and a capacitor to pin # 5) Socket - Red wire connected to pin 1 and to + supply.
Pin #5 - (internal - White/Black stripe and a capacitor to pin # 4) Socket - Black wire connected to Pin #6 and to pin #8 and probably to - voltage.
Pin #6 - (internal - Black wire) Socket - Black wire connected to Pin #5 and to pin #8 and probably to - voltage.
Pin #7 - (internal - Yellow wire) Socket - 1,000 ohm resistor to Pin #8 and to Blue/orange stripe wire, probably the RF output.
Pin #8 - (internal - bare wire soldered to the metal case) Socket - Other end of the 1,000 ohm resistor and to pins #5 and #6. Probably to (-) voltage.

OK, my observations a
Pins #1 and #4 are connected to a Plus voltage.. probably +12 or more..
Pin #3 maybe a 'keep-warm' supply which powers the oven when the equipment is turned off. (just guessing here)
Pins #5, #6 and #8 are Grounded and connected to the Minus voltage.
Pin #7 is the 1000.000KC output. It is loaded by the 1,000 ohm resistor.

What I will do when I have some time is to slowly increase the voltage to the oven/oscillator until there is an output on an oscilloscope.
That should b a good clue as to what actual voltage was required by the manufacturer.

I would like to use mine with a short-wave radio as the marker.
Good Luck
Eric.